It is known that the presence of magnetic materials on board a ship renders it detectable and identifiable by means for detecting its magnetic signature, usually called magnetic anomaly detectors. These detection means can for example be carried on board a ship, a mine, a torpedo, a missile, or an aircraft.
The use of nonmagnetic materials for limiting the magnetic signature of a ship is known. However, ferromagnetic materials do remain on board. For cost reasons, it appears preferable to make a ferromagnetic metal hull and to generate magnetic fields that compensate those connected to the hull itself using field sensors (magnetometers) installed inside the ship and immunization loops.
However, to achieve this compensation, it is necessary first to determine the magnetization of the hull. Once this magnetization is known, the currents, in each of the immunization coils, needed for this compensation can be determined.